For many years, die sets of the type used in machine presses to mount and guide mating die parts for movement toward and from one another during reciprocation of the press have included a ball bearing retainer or cage arranged for telescoping reciprocation between relatively reciprocating shaft and bushing members. The balls carried by the retainer are slightly larger in diameter than the annular space between the shaft and bushing members, so that the balls are under a forced fit, or are compressed slightly, between the shaft and bushing members to thereby insure exact alignment of the die parts carried in the die set. See, for example, U.S. Pat. No. 2,422,774 issued June 24, 1947 to Conner.
While the so-called compression loaded ball bearing die sets were capable of excellent performance over an extended period of time, they were, nevertheless, subject to wear due to the tendency of the balls to track or form lines of wear on the relatively engaged surfaces of the shafts and bushings. Several attempts have been made to distribute the wear caused by the pressure engagement of the ball bearings with the opposing surfaces of the shafts and bushings. For example, the ball bearings were mounted in helical array within their retainer or cage, or in a pattern, so that no two balls followed the same track along the shaft and bushing during relative reciprocation thereof. Also, attempts were made to provide an assembly in which the ball bearing retainer was free to rotate as well as reciprocate on the shaft member upon removal of the shaft and retainer from the bushing. For example, U.S. Pat. Nos. 2,774,430 and 2,846,278 to William J. Blazek and No. 3,357,755 to Danly disclose reciprocating ball bearing assemblies for use in die sets, wherein the ball bearing retainers are free to rotate as well as to reciprocate with respect to the associated shaft and bushing components when the shaft is removed from the bushing. However, the constructions proposed by each of these prior art patents were comparatively complicated and greatly increased costs of production of the bearing assemblies.